A. Treatment of Spinal Disc Abnormalities
Intervertebral disc abnormalities are common in the population and cause considerable pain, particularly if they affect adjacent nerves. Disc abnormalities result from trauma, wear, metabolic disorders and the aging process and include degenerative discs, localized tears or fissures in the annulus fibrosus, localized disc herniations with contained or escaped extrusions, and chronic, circumferential bulging discs. Disc fissures occur as a degeneration of fibrous components of the annulus fibrosus. Rather minor activities such as sneezing, bending or simple attrition can tear degenerated annulus fibers and create a fissure. The fissures may be further complicated by extrusion of nucleus pulposus material into or beyond the annulus fibrosus. Difficulties can still present even when there is no visible extrusion, due to biochemicals within the disc irritating surrounding structures and nerves. Initial treatment includes bed rest, pain killers and muscle relaxants, but these measures rarely correct the underlying cause. Surgical treatments include reduction of pressure on the annulus by removing some of the interior nucleus pulposus material by percutaneous nucleotomy. Surgical treatments meant to cure the underlying cause include spinal fusion with screws, rods and fusion cages. Devices and procedures involving screws, rods and plates are disclosed in the following U.S. patents, as well as others: Errico U.S. Pat. Nos. 37,665; 5,733,286; 5,549,608; 5,554,157; 5,876,402; 5,817,094; 5,690,630; 5,669,911; 5,647,873; 5,643,265; 5,607,426; 5,531,746 and 5,520,690; Metz-Stavenhagen U.S. Pat. No. 6,261,287; Puno U.S. Pat. No. 5,474,555; Byrd U.S. Pat. No. 5,446,237; Biedermann U.S. Pat. Nos. 5,672,176 and 5,443,467; Cotrel U.S. Pat. Nos. 4,815,453 and 5,005,562; Jackson U.S. Pat. No. 5,591,165; Harms U.S. Pat. Nos. 4,946,458; 5,092,867; 5,207,678 and 5,196,013; Mellinger U.S. Pat. No. 5,624,442; Sherman U.S. Pat. Nos. 5,885,286; 5,797,911 and 5,879,350; Morrison U.S. Pat. No. 5,891,145; Tatar U.S. Pat. No. 5,910,142; Nicholas U.S. Pat. No. 6,090,111; and Yuan U.S. Pat. No. 6,565,565. Fusion cages and related procedures are disclosed in Bagby U.S. Pat. No. 4,501,269; Michelson U.S. Pat. Nos. 5,015,247 and 5,797,909; Ray U.S. Pat. No. 6,042,582 and Kuslich U.S. Pat. Nos. 5,489,308; 6,287,343 and 5,700,291. Proposed disc replacement devices are disclosed in the following U.S. patents: Middleton U.S. Pat. No. 6,315,797; Marnay U.S. Pat. No. 5,314,477; Stubstad U.S. Pat. No. 3,867,728; Keller U.S. Pat. No. 4,997,432; and Buettner-Janz U.S. Pat. No. 4,759,766.
A contained disc herniation is not associated with free nucleus fragments migrating to the spinal canal. However, a contained disc herniation can still protrude and irritate surrounding structures, for example by applying pressure to spinal nerves. Escaped nucleus pulposus can chemically irritate neural structures. Current treatment methods include reduction of pressure on the annulus by removing some of the interior nucleus pulposus material by percutaneous nucleotomy. See, for example, Kambin U.S. Pat. No. 4,573,448. Complications include disc space infection, nerve root injury, hematoma formation, instability of the adjacent vertebrae and collapse of the disc from decrease in height. It has been proposed to treat weakening due to nucleus pulposus deficiency by inserting preformed hydrogel implants. See, Ray U.S. Pat. Nos. 4,772,287; 4,904,260 and, 5,562,736 and Bao U.S. Pat. No. 5,192,326.
Circumferential bulging of the disc also can result in chronic disc weakening. The joint can become mechanically less stable. As the bulging disc extends beyond its normal circumference, the disc height is compromised and nerve roots are compressed. In some cases osteophytes form on the outer surface of the disc and further encroach on the spinal canal and channels through which nerves pass. The condition is known as lumbar spondylosis. Continued disc degeneration can resulting in one vertebral body segment approaching and possibly contacting an adjacent vertebral body segment.
Treatment for segmental instability include bed rest, pain medication, physical therapy and steroid injection. Spinal fusion is the final therapy performed with or without discectomy. Other treatment includes discectomy alone or disc decompression with or without fusion. Nucleotomy can be performed by removing some of the nucleus matter to reduce pressure on the annulus. Complications include disc space infection, nerve root injury, hematoma formation, and instability of adjacent vertebrae. New fixation devices include pedicle screws and interbody fusion cages. Studies on fixation show success rates between 50% and 67% for pain improvement, and a significant number of patients have more pain postoperatively.
Delivery of tissue adhesives to the spine in a minimally invasive manner have been disclosed, and include procedures for restoring structural integrity to vertebral bodies. See Scribner U.S. Pat. Nos. 6,241,734 and 6,280,456; Reiley U.S. Pat. Nos. 6,248,110 and 6,235,043; Boucher U.S. Pat. No. 6,607,554 and Bhatnagar U.S. Pat. No. 6,395,007. Methods of repairing the spinal disc or portions thereof are disclosed in Cauthern U.S. Pat. No. 6,592,625, Haldimann U.S. Pat. No. 6,428,576, Trieu U.S. Pat. No. 6,620,196 and Milner U.S. Pat. No. 6,187,048.
B. Surgical Approaches to the Spine
The spine may be approached in open surgery using posterior, anterior or lateral approaches. The following is a brief description of several proposed surgical approaches which may be used to gain access to the spine in a less invasive manner to treat spinal insufficiency.
Posterior Lateral Approach Methods for disc access include laminectomy, a procedure wherein a channel is made from the dorsal side of the patient's back to the lumbar lamina of the disc. Blood vessels, ligaments, major back support muscles and spinal nerves located around the dural sac are retracted. Once the channel has been cleared, the standard procedure is to cut a hole in the disc capsule and pass instruments into the disc interior. This approach creates a defect that is oriented toward spinal nerves, thus typically the nucleus is completely removed to prevent extrusion of nuclear material and subsequent pressure on these nerves. Alternatively, under visual magnification with an operating microscope or operating loupe, small diameter microsurgical instruments can access the disc without cutting bone. It is possible to bypass the nerves and blood vessels entirely by inserting a cannula through the patient's side above the pelvic crest to reach a predetermined position along the lumbar portion of the spine. This procedure can be guided with use of fluoroscopy.
Kambin U.S. Pat. No. 4,573,448 describes a posterior lateral approach performed under local anesthesia by the insertion of a cannulated trocar over a guide wire extending through the patient's back toward a target disc at an angle of approximately 35 degrees with respect to the patient's perpendicular line. In particular, a hollow needle with a stylet is inserted at a location spaced from the midline so as to form a 35 degree angle in an oblique direction. When the needle reaches the annulus fibrosis it is withdrawn after a guide wire is introduced through the needle to the disc. A cannulated, blunt-tipped trocar is passed over the guide wire until the tip reaches the annulus. The guide wire is withdrawn. A closely-fitting, thin-walled cannula is passed over the trocar until it reaches the annulus. The trocar can be withdrawn. Cutting instruments or a punch can be used to expose the nucleus.
Paramedian Transabdominal Procedure In this procedure the patient is in the supine or lithotomy position. This transabdominal procedure involves splitting the paramedian rectus, retracting the bowel, incising the peritoneum on the posterior wall of the abdominal cavity and accessing the anterior spine. Alternatively, the anterior rectus sheath is exposed of the left rectus muscle. The anterior rectus sheath is incised to expose the body of the rectus muscle. The rectus muscle is then mobilized over an adequate length, preferably symmetrical with the incision, and the rectus is retracted medially. The posterior rectus sheath is cut to expose the peritoneum. The peritoneum is pushed aside and dissected to expose the psoas muscle. The ureter and the left iliac vessels are mobilized. The rectus muscle, ureter, iliac vessels, and peritoneum are retracted laterally to expose the lumbar region. For repair to lumbar vertebrae L3-4 and L4-5, access should be made to the left of the aorta and inferior vena cava, between the aorta and the psoas muscle, and through the posterior peritoneum and fatty tissue. In some cases it may be necessary to transverse the psoas muscle. For access to sites between L5 and S-1, the dissection is closer to the midline between the iliac branches of the great vessels.
Lateral Retroperitoneal Procedure The retroperitoneal procedure involves placing the patient in the right lateral recumbent position and making an incision in the abdomen at the border of the rectus muscle and subsequent dissection down to identify the peritoneum. Dissection can be performed bluntly or may be facilitated using a balloon cannula or expanding cannula as described by Bonutti (U.S. Pat. No. 5,514,153). The resulting retroperitoneal cavity can be held open with a retractor positioned to elevate the wall of the cavity adjacent to the patient's left side. The retractor may be a balloon retractor, see for example Moll U.S. Pat. No. 5,309,896 and Bonutti U.S. Pat. Nos. 5,331,975; 5,163,949; 6,277,136; 6,171,236; and 5,888,196. The peritoneum is dissected away from the abdominal wall in first a lateral and then a posterior direction until the spine is exposed. Under endoscopic visualization the iliopsoas muscle is dissected or retracted to facilitate disc repair.
Alternatively, dissection of the peritoneum can be accomplished using gas pressure into the preperitoneal and retroperitoneal space, thereby expanding the space and dissecting the peritoneal lining from the abdominal wall while relocating the peritoneal lining toward the midline of the abdomen. Access devices that may be used to gain minimally invasive access to the spine in several of the foregoing surgical approaches to the spine include expanding cannula structures such as Dubrul U.S. Pat. Nos. 5,183,464 and 5,431,676, Bonutti U.S. Pat. Nos. 5,674,240 and 5,320,611, and Davison U.S. Pat. Nos. 6,652,553 and 6,187,000.
Laparoscopic Approach It is also known to approach the lumbar spine anteriorly using a laparoscopic approach. See, for example, Green U.S. Pat. Nos. 5,755,732 and 5,620.458. Techniques for laparoscopic placement of spinal fusion cages are shown and described in Kuslich U.S. Pat. No. 5,700,291 and Castro U.S. Pat. No. 6,004,326. Implementing the laparoscopic approach requires that one or more laparoscopic access devices, commonly referred to as trocars (see for example Moll U.S. Pat. Nos. 4,601,710 and 4,654,030) be introduced into the abdominal cavity and that the cavity be insufflated to create working space. A laparoscope is inserted through one of the trocar ports to provide visualization of the abdominal cavity and surgical instruments may be introduced either through another trocar port or through a working channel of the laparoscope to dissect, manipulate and retract tissue to gain access to the posterior wall of the abdomen adjacent to the spine. Retractors, including balloon retractors, may be used to retract organs and tissue to maintain a clear working path. Care is taken to avoid damage to the major blood vessels, the aorta and femoral arteries, and the posterior wall of the peritoneum is opened to access the desired spinal vertebral body or disc segment.
C. Imaging Techniques
A variety of tools exist to assist the surgeon in assuring the desired access and treatment are achieved without compromising or adversely affecting adjacent healthy tissue. Treatment of the spine is usually planned based on CT or MR scans and fluoroscopy is commonly used during surgery to assure proper positioning and placement of surgical tools and devices. Image guided spinal surgery has been proposed and is contemplated for use with the surgical treatments proposed herein. See, for example, Cosman U.S. Pat. Nos. 5,662,111; 5,848,967; 6,275,725; 6,351,661; 6,006,126; 6,405,072; Bucholz U.S. Pat. Nos. 5,871,445; 5,891,034; 5,851,183; and Heilbrun U.S. Pat. Nos. 5,836,954 and 5,603,318. The position of instruments typically is detected using a camera and markers on the surgical tool, and an image of the working portion of the instrument is super-imposed upon a pre-operative image, such as a CT, MRI or ultrasound image to show the surgeon where the working instrument is located relative to anatomical landmarks and the tissue to be treated. As imaging techniques and equipment improve, it is contemplated that image guided surgery will evolve to using real time intraoperative images and that the position of the surgical instrument will be shown relative to these real-time intra-operative images in addition to or in place of pre-operative images.
D. Adhesives and Other Repair Materials.
Numerous patents describe previous approaches to disc repair. These include U.S. Pat. No. 6,332,894, Stalcup et al., which describes an orthopedic implant for implanting between adjacent vertebrae comprising an annular bag and a curable polymer and hard particulate with the bag. The polymer is cured after implantation to make it harder and to fuse the hard particulate into a single mass. U.S. Pat. No. 6,264,659, Ross et al., describes a process of injecting a thermoplastic material within an annulus fibrosis of a selected intervertebral disk. U.S. Pat. No. 6,127,597, Beyar et al., describes a solid phase formation device for orthopedic application. The expandable device includes a material that polymerizes after implantation. U.S. Pat. No. 6,419,706, Graf, describes a disc prosthesis comprising a preformed polymer core surrounded by a rigid material coating. U.S. Pat. No. 6,569,442, Gan et al., describes a polymer foam prepared outside the body for intervertebral disc reformation.
U.S. Pat. No. 6,022,376, Assell et al., describes a capsule-shaped prosthetic spinal disc nucleus for implantation into a human intradiscal space, made of a substantially inelastic constraining jacket surrounding a pre-formed amorphous polymer core. U.S. Pat. No. 6,132,465, Ray et al., describes a device similar to the device described in U.S. Pat. No. 6,022,376 with certain shape modifications. U.S. Pat. No. 6,306,177, Felt et al., describes an in situ polymerizing fluid used in tissue repair in the absence of a constraining structure, such as a balloon. The polymerizing materials comprise a quasi-prepolymer component and a curative component containing chain extenders, catalysts and the like. U.S. Pat. No. 4,743,632, Marinovic, discloses the use of a two-part adhesive for use in surgery, where a diisocyanate material is mixed with a polyamine or similar material to produce an in situ cure. Preferred materials are described in our U.S. Pat. No. 6,254,327, and our pending applications US 2003-0135238 and US-2004-0068078.
E. Other References providing Background Information.
These include U.S. Pat. No. Re. 33,258 (Onik et al.), U.S. Pat. No. 4,573,448 (Kambin), U.S. Pat. No. 5,192,326 (Bao et al.), U.S. Pat. No. 5,195,541 (Obenchain), U.S. Pat. No. 5,197,971 (Bonutti), U.S. Pat. No. 5,285,795 (Ryan et al.), U.S. Pat. No. 5,313,962 (Obenchain), U.S. Pat. No. 5,514,153 (Bonutti), U.S. Pat. No. 5,697,889 (Slotman et al.), U.S. Pat. No. 5,755,732 (Green et al.), U.S. Pat. No. 5,772,661 (Michelson), U.S. Pat. No. 5,824,093 (Ray et al.), U.S. Pat. No. 5,928,242 (Kuslich et al.), U.S. Pat. No. 6,004,326 (Castro et al.), U.S. Pat. No. 6.187,048 (Milner et al.), U.S. Pat. No. 6,226,548 (Foley et al.), U.S. Pat. No. 6,416,465 (Brau), WO 01/32100, and FR 2 639 823.